The present invention relates generally to telecommunications systems, and more particularly, to a system for interfacing telephony devices with packet based networks.
Telephony devices, such as telephones, analog fax machines, and data modems, have traditionally utilized circuit switched networks to communicate. With the current state of technology, it is desirable for telephony devices to communicate over the Internet, or other packet based networks. Heretofore, an integrated system for interfacing various telephony devices over packet based networks has been difficult due to the different modulation schemes of the telephony devices. Accordingly, it would be advantageous to have an efficient and robust integrated system for the exchange of voice, fax data and modem data between telephony devices and packet based networks.
In accordance with one aspect of the present invention, a method of compensating a signal includes averaging the signal in a first phase, and combining the average signal with the signal in a second phase.
In another aspect of the present invention, a method of timing recovery includes receiving a signal having a data rate, sampling the signal at a sampling rate, estimating a timing error between the data rate and the sampling rate, averaging the estimated timing error during a first phase, combining the averaging estimated timing error with the estimated timing error during a second phase, and adjusting the sampling rate as a function of the combined averaging estimated timing error and the estimated timing error.
In yet another aspect of the present invention, a method of timing recovery includes receiving a signal at a data rate, sampling the signal at a sampling rate, measuring a phase error between the data rate and the sampling rate, estimating a frequency error between the data rate and the sampling rate during a first phase, combining the phase error and the frequency error during a second phase, and adjusting the sampling rate as a function of the combined frequency error and phase error.
In a further aspect of the present invention, a signal compensator includes an estimator which a estimated an average of the signal in a first phase, and a combiner which combines the signal with the estimated average signal in a second phase.
In yet a further aspect of the present invention, a timing recovery system includes a sampler capable of sampling a signal at a sampling rate, the signal having a data rate, a timing error estimator which estimates a phase error between the data rate and the sampling rate, a frequency offset estimator which estimates a frequency error between the data rate and the sampling rate during a first phase, a combiner which combines estimated phase error and the estimated frequency error during a second phase, and a clock adjuster which adjusts the sampling rate of the sampler as a function of the combined estimator frequency error and estimator phase error.
In still yet another aspect of the present invention, a data transmission system includes a telephony device which outputs a signal having a data rate, a data exchange coupled to the telephony device, the data exchange having a sampler capable of sampling the signal at a sampling rate, a timing error estimator which estimates a phase error between the data rate and the sampling rate, a frequency offset estimator which estimates a frequency error between the data rate and the sampling rate during a first phase, a combiner which combines the phase error and the estimated frequency error during a second phase, and a clock adjuster which adjusts the sampling rate of the sampler as a function of the combined estimated frequency error and estimated phase error.
In still yet a further aspect of the present invention, a signal compensator includes estimation means for estimating an average of the signal in a first phase, and combining means for combining the signal with the estimated average signal in a second phase.
In an alternative aspect of the present invention, a timing recovery system includes sampling means for sampling a signal at a sampling rate, the signal having a data rate, phase error estimation means for estimating a phase error between the data rate and the sampling rate, frequency error estimation means for estimating a frequency error between the data rate and the sampling rate during a first phase, combining means for combining the estimated phase error and the estimated frequency error during a second phase, and clock adjusting means for adjusting the sampling rate of the sampler as a function of the combined estimated frequency error and estimated phase error.
In another aspect of the present invention, computer-readable media embodying a program of instructions executable by a computer performs a method of compensating a signal, the method includes averaging the signal in a first phase, and combining the average signal with the signal in a second phase.
In yet another aspect of the present invention, computer-readable media embodying a program of instructions executable by a computer performs a method of timing recovery, the method including receiving a signal having a data rate, sampling the signal at a sampling rate, estimating a timing error between the data rate and the sampling rate, averaging the estimated timing error during a first phase, combining the averaged estimated timing error with the estimated error during a second phase, and adjusting the sampling rate as a function of the combined averaged estimated timing error and the estimated timing error.
In still yet another aspect of the present invention, computer-readable media embodying a program of instructions executable by a computer performs a method of timing recovery, the method including receiving a signal at a data rate, sampling the signal at a sampling rate, measuring a phase error between the data rate and the sampling rate, estimating a frequency error between the data rate and the sampling rate during a first phase, combining the phase error and the frequency error during a second phase, and adjusting the sampling rate as a function of the combined frequency error and phase error.
It is understood that other embodiments of the present invention will become readily apparent to those skilled in the art from the following detailed description, wherein it is shown and described only embodiments of the invention by way of illustration of the best modes contemplated for carrying out the invention. As will be realized, the invention is capable of other and different embodiments and its several details are capable of modification in various other respects, all without departing from the spirit and scope of the present invention. Although the the timing recovery system is described in the context of a data exchange, those skilled in the art will appreciate that the timing recovery system is likewise suitable for various other telephony and telecommunications application. Accordingly, the drawings and detailed description are to be regarded as illustrative in nature and not as restrictive.